Properi;'  of »'"°  I'rv  °d  si 


Circular  no   SO. 


United  States  Departmenl  of  \gr 

BUREAU    OF    KNTOMOLOGY, 

L.    n     M'>W*KH     Kntomologto   und   Our! 


III     ^^  111  I  I     I'lM     \\l  I  \  II  . 


D.  Hopkins, 

i^t  urn 


The  Bureau  of  Entomology  has  been  conducting  systematic  ana  eco- 
nomic investigations  "f  the  weevils  infesting  the  bark  of  the  trunk  and 
terminal  shoots  of  conifers  in  the  United  States,  the  results  of  which  will  be 
published  in  the  regular  technical  and  popular  bulletins;    bul  Bince 


Fid    l  Her  I'lL-im-  Datura  I    Hue  at 

i  iult  KbowitlR  inituriil  mil  ' 

can  not  be  issued  in  time  t"  be  of  Bervice  this  Beason,  this  circular 
has  been  prepared  to  give  the  information  Which  is  of  immediate  prac- 
tical  importance  in  regard  to  one  of  the  mosl  destructive  of  these  weevils. 

I  Hi:    l\-i:<  T    \M>   ITS    H  IBITS. 

The  white-pine  weevil  is  a  Bomewhat  elongate,  brownish  Bnout  beetle, 
l  to  5  nun.  in  length,  having  the  thorax  and  elytra  marked  with  irr»  u'- 
ular  spot-  of  brown  and  white  -  1,  </).     The  winter  is  p 

in  the  adult  si  ridently  in  the  ground.     The  beetles  come  out  of 

their  winter  quarters  and  By  early  in  May.  and  after  feeding  for  a  few 
days  on  the  hark  of  the  living  white-pine  terminal  shouts  deposit  their 


■  \  Peck;  Order  Coleoptera,  Family  Carcnlion 


eggs  in  punctures  in  the  bark  of  the  shoot  of  the  previous  year's  growth, 
placing  one  or  two  eggs  in  a  pit  or  cavity  in  the  inner  bark  made  by 

the  beak  of  the  mother  beetle.  In 
from  .six  to  ten  days  the  eggs  begin 
to  hatch  into  small  white  grubs 
(larva),  which  at  first  arc  usually 
found  in  large  numbers  feeding 
upon  the  inner  hark  and  cambium 
(see  fig.  2).  They  usually  work 
downward  and  sometimes  extend 
their  work  into  the  hark  of  the 
2-year-old  stem  and  base  of  the 
branches.  By  the  time  the  larva: 
have  completed  their  development 
(fig.  1,  h)  they  are  greatly  reduced 
in  numbers  by  natural  enemies  and 
other  causes.  The  survivors  bur- 
row into  the  wood  or  pith  of  the 
terminal  and  excavate  individual 
transformation  cells,  which  they 
line  and  cover  with  excelsior-like 
borings.  In  these  cells  they  trans- 
form to  pupa1  (see  fig.  1,  c)  and 
adults,  and  during  July  and  August 
of  the  same  year,  when  the  adults 
are  fully  matured,  they  bore  their 
way  out  and  seek  suitable  places 
in  which  to  pass  the  winter. 

LONG    LI1T.    (iK    THE    ADULT. 

From  recorded  observations  on 
some  species  of  Pissodes  or  bark 
weevils  by  investigators  in  Europe, 
and  on  representatives  of  other 
allied  forms  in  Europe  and  in  this 
country,  it  appears  that  an  indi- 
vidual adult  may  live  two  or  three 
years  and  will  deposit  eggs  each 
year. 

SEASONAL    BISTORY. 


Km 


-White  pine  weevil:  Newly  hatched  larvi 


The  beetles  are  active  from  about 
.n  work  in  riBorous  terminal  shoot  of  white  t],(,  ]s(  fc0  the  loth  of  Mavor  later, 
pine    (Author's  illustration.)  . 

depending  on  local  conditions  and 

weather.      Eggs  are  evidently  deposited  during  the  principal  activity  of 
the  adults,  possibly  during  the  greater  part  of  the  month  of  May.      The 


•  I  of  development  of  the  larvae  varies  greatly.    Those  more  fortu« 

n.it. •  in  Becuring  a  continuous  I i  Bupply  ma)  become  fully  developed 

before  8 e  of  the  lesa  fortunate  ones  in  the  same  terminal  are  one 

fourth  as  large,  although  the  i  •.-  from  which  both  came  maj  have  been 
deposited  at  aboul  the  Bame  time.  There  ie  also  .1  wide  range  in  the 
period  of  transformation  to  the  pupa  and  adults  and  again  in  the  emer- 
gence of  the  latter.  Thus,  it'  the  Brsl  1  deposited  aboul  the  v'h 
ofMayal  (Kilford,  Pa.,  latitude  ll  20\  altitude  500  to  1,000  feet,  the 
will  begin  ti>  hatch  aboul  the  1  Itli  of  May,  the  Brsl  larva-  will 
be  full  grown  aboul  July  s.  the  first  transformations  to  the  pupa  will 
take  place  about  the  15th  of  July,  the  first  adults  will  begin  t"  emerge 
about  July  25,  and  adults  will  continue  to  come  out  until  tin-  first  part 
of  September.  Practically  all  will  be  out  by  September  I 5.  The  prin- 
cipal period  of  emergence,  however,  is  from  about  the  25th  of  July  t<> 
the  middle  of  August. 

KINDS   OF   TREES    \  IT  iCKED. 

The  white  pine  is  the  tree  normally  attacked,  but  the  weevil  is  occa- 
sionally found  in  the  terminals  or  topmost  branches  of  the  native  and 
cultivated  spruces,  the  jack  pine,  and  very  rarely  in  the  pitch  pine  or 
other  eastern  piti<~ .  The  attack  is  confined  to  the  small  to  large  Bap- 
ling  and  pole  stages  in  the  development  of  the  tri 

DISTRIBUTION. 

Our  records  indicate  thai  this  weevil  follows  the  natural  range  of  the 
white  pine  from  southwestern  North  Carolina  into  New  Brunswick  and 
Canada  and  westward  int . >  Wisconsin. 

i:\  [DEN<  1:   OF    ATTACK. 

The  Brat  evidence  of  attack  on  the  living  terminals  is  the  exudation 
of  fresh,  clear,  and  shining  drops  of  resin.     Upon  closer  examination 

fresh    pinhole-like   puncture-,  are    found    in  the  hark    (t  §  ml  at  the 

same  time  the  inconspicuous  beetles  maj  be  found  on  the  terminal  ;  but 
upon  the  approach  of  the  observer  the  beetles  will  often  let  go  their 

foothold  and  fall  to  the  ground,  where  they  will  feign  death.  In  a  few 
day-  after  the  first  attack  the  injured  terminals  will  have  the  resin 
more  or  less  abundanl  and  conepicuous  over  the  greater  part  of  the  sur- 
face. The  first  evidence  that  the  terminals  are  infested  with  larva-  is 
the  stunted,  unhealthy  appearance  of  the  young  growth  at  the  tip. 
which  will    gradually  die.   the    m  turning   yellowish    and    later 

brownish. 

The  time  of  development  of  the  broods  to  adults  will  he  indicated  by 
the  lirst  appearance  of  dead  tips. 

Did  work  of  the  weevil  is  evidenced  by  the  1  of  old  dead  ter- 


Pig.  8.— Work  of  white-pine  weevil,  showing  character  oi  injury,  chip  cocoons,  and  pupal  cells: 
a,  Vigorous  terminal  shoot,  Bhowing  condition  of  nev  growth  at  time  pupa'  are  transforming 
to  adults;  b.  8-year-old  top,  showing  how  larvae  have  migrated  from  terminal  to  the  2  and  3 
year  old  Internodea  ;  e,  chip  cocoon  ami  pupal  cell,  natural  size.    (Original.) 


minala  in   the  forks 
< .  f    the    young    In 
(fig.   I),  and  ill"  re 
suits   of   their   work 

will  lie  evident  ill  the 

deformed    ^  ro  \\  t  li . 

f  <>rk  >  .      and 

broad,  low  crow  n.»  ol 
both  young  ami  old 
trees  ( t i lx .  5). 

CHARACTER    "i     THE 
DAMAGE. 

'I'lir  damage  and 
loss,  as  affecting  the 
commercial  tree,  con- 
i  not  only  in  the 
death  of  the  terminal 
•dioots,  hut   in  Mlh>e- 

quent  abnormal  de- 
velopment    of    t  li e 

trees  BO  injured.    The 

dying  of  the  leading 
shoot  throws  the  next 
year's  growth  into  the 
Upper  lateral  -hoot-. 
which  results  in  a 
forked  and  many- 
branched  top.  Each 
branch    produces    a 

vigorous  terminal, 
and  all  compete  for 
leadership  in  forming 
the  crown.  In  BUC- 
Ceeding  years  the 
more  vigorous  termi- 
nals of  the  topmost 
branches  are  at- 
tacked and  killed. 
causing  morebranch- 
and  thus  effec- 
tually preventing  the 
development  of  the 
normal  straight  trunk 
and  symmetrical  crown  necessary  to  a  tree  ot  commercial  value. 


initial 


I 


EXTENT  OP  DAMAGE. 
The  extent  of  damage,  as  affecting  natural  reproduction,  planta- 
tions, and  tim- 
ber of  commer- 
cial size  in  the 
forest,  is  difficult 
to  estimate ;  but 
it  is  an  impor- 
tant item  to  be 
charged  to  the 
losses  in  com- 
mercial growth 
of  white  pine  and 
is  therefore  a  for- 
estry problem 
which  must  de- 
mand special  at- 
tention in  the 
future  manage- 
ment of  wood- 
lots  and  forests, 
wherever  the  tree 
predominates. 

FAVORABLE      AND 

0 X F A  V OKABLE 
CONDITIONS  FOR 

DESTRUCTIVE 
WORK  BY  THE 
WEEVIL. 

The  most  fa- 
vorable condi- 
tion for  serious 
injury  by  this 
weevil  consists 
in  a  scattering  or 
open  pure  stand 
of  young  white 
pine  where  the 
growth  is  healthy 
and  rapid,  such 
as  is  found  in 
open  planta- 
tions,   in    aban- 

...     r    „7    ,    ,    , .  doned  fields,  and 

Fig.  5.— Work  of  white-pme  weevil, showing  result  of  killed  terminal 

shoot  in  8-year-old  top  of  large  sapling.     (Original.)  around    the    bor- 


.,,  dense  stands  wherever  the  Boil  and  other  conditions  are  moal 
favorable  for  rapid  growth. 

The  unfavorable  conditions  for  injury  are  bIom  growth,  dense  pure 
stands,  and  mixed  Btande  of  pine  and  hardwood. 

Under  the  former  conditions  the  thriftj .  vigorous  terminals  are  espe- 
cially fuvored  as  breeding  placee  for  the  weevil ;  and  where  these  are 
Killed,  the  vital  energ}  of  the  tree  i  thrown  into  the  lateral  branches. 
Open  stands,  then  fore,  favor  the  developmenl  ol  large  branches  and  a 
spreading  crown,  while  under  conditions  unfavorable  to  weevil  injury 
the  terminals  are  Bmaller  and,  even  if  they  are  killed,  the  close  Btand  or 
lateral  Bhade  will  tend  to  produce  an  upward  or  vertical  growth  of  the 
topmost  branches,  the  stronger  one  taking  the  lead  and  Boon  repairing 

the  damage. 

\  vn  i;  \i.   ENEMIES. 

Numerous  parasitic  and  predatorj  insect  energies  attack  the  develop- 
ing broods  in  the  terminals.     Woodpeckers,  ed  on  the  matured 


terminals!  II.  with  win  erendallow- 

larva>,  pupa1,  and  adults.  Some  of  the  larva'  apparently  die  from 
3e,  and  when  large  numbers  of  them  are  crowded  together  the 
larger  ones  appear  to  feed  on  the  -mailer  ones,  bo  thai  on  the  average 
not  more  than  from  3  to  5  per  cenl  of  the  hatched  larvae  ever  reach 
maturity  and  emerge  from  the  infested  terminals.  However,  each 
female  is  capable  of  depositing  more  than  one  hundn  each  year 

for  several  years;  thus  the  depredations  arc  continuous.  During  Borne 
years  the  damage  will  be  Blight,  while  in  other  years  it  will  be  very 
severe,  the  amount  of  injury  depending  on  the  number  of  adults  that 
survive  and   the  conditions  presented  for  their  attack  and  development. 

mi:  rin  >i»  i  >k  i  <  iNi'iv'i  'i  i. 

It   will  be  -ecu  that  in  the  successful  control  of  this  pest,  as  in  the 
control  of  forest  insects  in  general,  much  depend.-  on  Bpe<  ial  features  in 


UNIVERSITY  OF  FLORIDA 


8  3  1262  09216  4630 

the  general  methods  of  forest  management  which  will  hring  ahout 
unfavorable  conditions  for  injury  and  thus  prevent  loss. 

It  will  also  be  seen  how  important  it  is  to  know  the  principal  facts 
in  regard  to  the  life  history  and  habits  of  the  insect,  in  order  to  secure 
the  best  results  from  methods  of  management  and  of  direct  control. 

Heretofore  this  species  lias  been  confused  with  another  species  with 
very  different  habits,  and  some  of  the  published  data  and  recommen- 
dations based  on  such  confusions  are  of  no  value. 

The  white-pine  weevil  rarely,  if  ever,  passes  the  winter  in  the  termi- 
nals. The  present  evidence  indicates  that  it  never  breeds  in  the  thick 
hark  on  the  trunks  and  stumps  of  the  white  pine  or  other  pines;  thus 
it  can  not  he  trapped  in  the  trunks  of  felled  and  girdled  pine. 

DESTRUCTION    OF   THE    BROODS. 

The  only  practical  method  of  destroying  the  weevil  appears  to  be  the 
treatment  of  the  infested  terminals,  and  to  secure  the  best  results  spe- 
cial attention  must  be  given  to  certain  important  details. 

If  the  infested  terminals  are  cut  or  broken  during  June  and  July  and 
burned,  the  broods  of  the  weevil  will  he  effectually  destroyed,  but  vast 
numbers  of  natural  enemies  will  also  be  destroyed.  A  better  method 
is  to  collect  the  terminals  during  the  first  half  of  July  before  the  beetles 
begin  to  emerge  and  to  place  them  in  tight  barrels  securely  covered 
with  wire  Hy-screen  netting  on  one  or  both  ends  (see  fig.  6).  The  bar- 
rels should  be  left  in  the  groves,  so  that  the  parasites  and  other 
enemies  may  escape,  while  the  beetles  perish.  After  the  1st  of  October 
the  weevils  will  all  be  dead,  and  the  netting  may  then  be  removed, 
although  the  barrels  with  their  contents  should  be  left  until  the  follow- 
ing June  to  allow  the  escape  of  the  later  developing  and  larger  parasites. 
The  barrel  should  not  he  placed  in  a  position  to  collect  rain.  It  is 
necessary,  however,  if  this  method  be  adopted,  that  it  he  repeated  two 
or  three  years  in  succession  in  the  same  locality,  in  order  to  catch  the 
successive  hroods  from  the  old  parent  beetles  that  live  over  from  pre- 
ceding years. 

NOTE. 

The  statements  and  recommendations  in  this  circular  are  based  on  recent 
observations  and  investigations  by  the  author  and  by  Field  Assistant  W.  F.  Fiske, 
and  serve  as  a  partial  revision  of  what  has  hitherto  been  published. 

Approved : 

James  Wilson, 

Seen  tiir;/  of  Agriculture. 

Washington,  1).  C,  May  21,  1907. 

O 


